The collection went away

I started building a lightroom collection. I grabbed the shots from my
Sept 2010 library, moved to the October library and the collection was
no longer in the collection tab. Is there any way of making a
collection of files that are in multiple libraries?
--
The first step is learning to take great photos,
the second step is learning to throw away ones that are merely good.
Larry Colen lrc at red4est.comhttp://www.red4est.com/lrc